Use C99-defined signbit macro

Merged: https://github.com/ruby/ruby/pull/4783

complex.c

@@ -34,10 +34,6 @@
 #else
 static VALUE RFLOAT_0;
 #endif
-#if defined(HAVE_SIGNBIT) && defined(__GNUC__) && defined(__sun) && \
-    !defined(signbit)
-extern int signbit(double);
-#endif
 
 VALUE rb_cComplex;
 

configure.ac

@@ -1916,17 +1916,7 @@ AS_CASE(["$target_os"],
 AC_CHECK_HEADERS(sys/pstat.h)
 
 
-AC_CACHE_CHECK(for signbit, rb_cv_have_signbit,
+AC_DEFINE(HAVE_SIGNBIT)         # C99; backward compatibility
-  [AC_LINK_IFELSE([AC_LANG_PROGRAM([[
-#include <math.h>
-]], [[int v = signbit(-0.0);]])],
-	rb_cv_have_signbit=yes,
-	rb_cv_have_signbit=no)])
-AS_IF([test "$rb_cv_have_signbit" = yes], [
-  AC_DEFINE(HAVE_SIGNBIT)
-], [
-  AC_LIBOBJ([signbit])
-])
 
 AC_FUNC_FORK
 

include/ruby/missing.h

@@ -198,10 +198,6 @@ RUBY_EXTERN size_t strlcpy(char *, const char*, size_t);
 RUBY_EXTERN size_t strlcat(char *, const char*, size_t);
 #endif
 
-#ifndef HAVE_SIGNBIT
-RUBY_EXTERN int signbit(double x);
-#endif
-
 #ifndef HAVE_FFS
 RUBY_EXTERN int ffs(int);
 #endif

math.c

@@ -26,11 +26,6 @@
 #include "internal/object.h"
 #include "internal/vm.h"
 
-#if defined(HAVE_SIGNBIT) && defined(__GNUC__) && defined(__sun) && \
-    !defined(signbit)
-    extern int signbit(double);
-#endif
-
 #define RB_BIGNUM_TYPE_P(x) RB_TYPE_P((x), T_BIGNUM)
 
 VALUE rb_mMath;

missing/signbit.c

@@ -1,19 +0,0 @@
-#include <limits.h>
-#include "ruby.h"
-
-int
-signbit(double x)
-{
-    enum {double_per_long = sizeof(double) / sizeof(long)};
-    enum {long_msb = sizeof(long) * CHAR_BIT - 1};
-    union {double d; unsigned long i[double_per_long];} u;
-    unsigned long l;
-
-    u.d = x;
-#ifdef WORDS_BIGENDIAN
-    l = u.i[0];
-#else
-    l = u.i[double_per_long - 1];
-#endif
-    return (int)(l >> long_msb);
-}